1. Field of the invention
The present invention relates to a new structure relating to small diameter atmospheric and vacuum distillation towers, and more particularly, to load-bearing structure within the tower.
2. Background Art
The internal structure of a distillation tower is attached and supported to the tower using a support ring. The support rings are used to seat packing structure, support grids, and hold down grids within the distillation tower.
The packing portion of the distillation tower generally includes a collection of tower packing materials which provide efficient contact between the liquid and the vapor. The packing generally occupies a relatively small volume, so that there is free space to permit a large throughput of vapor. The capacity of a tower is limited by several factors, involving void space and available tower diameter.
Small diameter distillation towers experience "flooding" at high capacities as calculated by using the inside tower diameter. Flooding occurs in the packing when the vapor bumps the liquid up and out of the packing sections. Such localized flooding is depicted in FIG. 2A wherein arrow L represents liquid flow, arrow V represents vapor flow, and F represents a region of localized flooding. Most of the flooding in these smaller distillation towers occurs in the immediate vicinity of the packing at the conventional support ring (see FIG. 2A). Increasing the void space at the support ring for a small diameter tower improves the column capacity and efficiency of the packed tower.
Conventional support rings in distillation towers are secured to the internal surface of the towers, and are used to support packing, hold-down grids, and other similar type loads (see FIG. 1A).
The conventional support ring is about three inches wide and is secured within the internal diameter of the tower. Typically, the ring consumes six inches of the inside diameter of the distillation tower. Hence, in smaller towers where the internal tower diameter is three feet or less, the size of the support ring represents a significant portion of the internal cross-sectional area of the tower.
The internal diameter of the tower is used for purposes of calculating the capacity and the efficiency of the tower. If, for example, the inside of the tower has a 2.50 foot diameter, the total cross-sectional area of the tower is about 4.91 square feet. If the tower uses a conventional three-inch support ring, the cross-sectional area of the tower is reduced to 3.14 square feet, or a reduction of about 35%. Hence, as demonstrated by this example, a two-and-a-half foot tower with the conventional support ring is equivalent to a two foot tower without the support ring.
What is needed is a new support ring apparatus for smaller distillation towers which has the load-bearing strength of the conventional support ring, but which does not cause the dramatic reduction in the cross-sectional area of the tower.